(1) Field of the Invention
The present invention relates to a fixing device and an image forming apparatus using the device, in particular relating to a fixing device for use in an image forming apparatus for forming images using toner based on electrophotography, such as an electrostatic copier, laser printer, facsimile machine or the like, as well as relating to an image forming apparatus using this device.
(2) Description of the Prior Art
Conventionally, image forming apparatuses based on electrophotography can form high quality images at a reasonable price with high reproducibility and excellent operativity so that they are used for copiers, printers, facsimile machines and multifunctional machines having two or more functions of these and others.
Recording media for use in these image forming apparatuses based on electrophotography may include paper, plastic film and sheet, etc. As one example of recording media, there is a lenticular lens sheet that is formed with lens-like meniscuses on a light transmissive base surface.
A lenticular lens is one that is used in a system called “lenticular system” in which a stereoscopic vision is made possible without using any special device. Use of this lenticular sheet makes it possible to provide a 3D image representation or change the image between multiple different images depending on the angle from which the image is viewed. An image combined with the lens is usually produced in the field of high-volume printing by laminating a light transmissive sheet formed with the lens on a printed image on paper or film.
There has been a disclosed electrophotographic technique in which a toner image is formed using a conventional lens sheet (a sheet with a jagged lenticular surface (see Japanese Patent Application Laid-open H08-22091).
However, the above prior art technology entails the problem that the jagged configuration of the lens sheet causes abnormal electric discharge and also produces stripe-like unevenness in the formed image due to steps of jaggedness.
In order to solve the above problem, there is a disclosure of a configuration in which a recording medium of a light transmissive, transparent substrate having one side formed with a thermoplastic resin layer for forming a lens layer and the other side formed with a thermoplastic image receiving layer, is formed with a toner image first, then formed on the lens-forming layer with a lens so as to produce a lenticular image (see Japanese Patent Application Laid-open 2008-26477).
However, in the above second patent document, the recording medium made of the lens forming layer, substrate and image receiving layer is formed on its receiving layer with a toner image, then the lens forming layer is heat pressed using a forming die so as to form a lenticular image having a lens layer. That is, since the recording medium having passed through the fixing process in which no heat deformation will take place is then subjected to a high-temperature pressing process to form a jagged lens surface, there is a high risk of the toner image being disordered, possibly causing degradation of the lenticular image. Further, the apparatus also entails the problems that not only the power consumption of the apparatus increases but also the apparatus itself becomes bulky.
There is also an idea that a lens layer may be formed using a transparent toner. However, in this case a separate developing vessel for the transparent toner is needed, resulting in a further enlargement of the apparatus. Moreover, the transparent toner is not only needed to have high light transmittance but also is required to have excellent heat processibility. However it is quite difficult for a powdery transparent toner to achieve both high heat processibility and preservation stability.